Abstract

Hydatid disease is anthropozoonosis with worldwide distribution due to the close association among sheep, dogs, and humans. It is a parasitic infestation by a tapeworm Echinococcus. It affects both humans and other mammals such as sheep, goats, horses, caribou, moose  etc. It can occur anywhere in the body. Giant cysts need radical therapy because they might lead to perforation and anaphylaxis in some patients. The patient was sent to ultrasound to rule out hepatomegaly.

A large hydatid cyst that covered part of medial aspect of the right  and left lobe of the liver of a 75 years old Vietnamese woman. This case shows the important of ultra-sonography of diagnosis complicated cysts in the liver. The cysts was proved to be hydatid cyst after surgery.

Case Report

Seventy five years old Vietnamese female with mild abdominal pain arrived to the ultrasound department for abdominal ultrasound to rule out hepatomegaly and ascites.

A complete abdominal ultrasound was done , a complex septated cystic mass covering most of the medial right side and left lobe of the liver was found.  The mass was predominately cystic and measuring 51 mm x43 mm x40 mm with some septation and smaller adjacent cyst measuring 10 mm by 11 mm . Other small calcification were also noted in the right lobe of the liver. The large cyst  contain mobile debris that caused false artifacts on color flow Doppler, and the cyst had no internal vascularity on color flow Doppler.

CT Scan was ordered and the mass was removed surgically, and proved to be a large hydatid liver cyst. The patent’s lived most of her life in the farm of one of Vietnam village before moving to Canada to join her children.

Introduction

Hydatid disease (HD) is a worldwide distribution including North Canada and North Europe.  In humans there are 3 different forms1-3:

1. Cystic (Unilocular Echinococcus) – most common form caused by E. granulosus.
2. Alveolar echinoccosis – caused by E. multilocularis.
3. Polycystic echinococcosis – caused by E vegeli.

Echinococcal disease is occasionally seen in immigrants and among the indigenous population of northern Canadian communities. Both Echinococcus granulosus and Echinococcus multilocularis infections are seen in Canada; however the definitive host for E.granulosus is the dogs, wolves, and possibly the fox, the intermediate host maybe the caribou or moose. It has been suggested by some authors that the sylvatic variant of the disease seen in North America is more benign than the post oral variant seen in countries traditionally considered to be sources of hydatid disease4-6.  Because humans play the same role of intermediate hosts in the tapeworm life cycle as sheep, humans also become infected by ingesting tapeworm eggs passed from an infected Carnivore 7.  

Pathophysiology

In  primary echinococcus, metacastodes develop from oncospheres after per oral infection with E. granulosus eggs. In primary echinoccosis larva cysts may develop in every organ. Most patients as many as 80% have single-organ involvement and harbor a solitary cyst.

Approximately two thirds of patients experience liver echinoccosis. The second most common organ involved is the lung7. The growth rate of cysts is highly variable and may depend on stain differences. The average increase of cysts diameter vary approximately 1-1.5cm/year 7.

Frequency

Realistic national international figures do not exist for total numbers of cases of cystic echinoccosis. However, the increasing use of mass screening with ultrasonography in endemic countries is generating important epidemiological data7. In the United States, transmission of  E.granulosus in the dog-sheep cycle is known to Zuni, Navajo, and Santo Domingo tribes, whose members live in close proximity to their animals. Utah has had the highest number of surgical cases of the western states with approximately 45 cases from 1944-1994 7.

Annual incidence rates of diagnosed human cases per 100,000 inhabitants vary widely from less than 1 case per 100,000. Cystic echinoccosis causes not only illness but also productivity losses in human and agricultural animal population, and it can have large societal impact on endemic areas 7.

Mortality/Morbidity

Cystic echinoccosis is rarely fatal. Occasionally deaths occurs because of anaphylactic shock or cardiac tamponade in the heart 8. Rare locations of the  hydatid cyst can be seen in the muscle, bone, brain, orbit , and can cause dramatic and disabling symptoms such as blindness, and paralysis 9-16.

Race

No racial predilection exists 17.

Sex

In some endemic countries females are affected more than males because their life style habits and practices bring them into contact with the parasite 17.

Age

Individuals of all ages are affected. In some endemic countries, children have higher infection rates because they are most likely to play with dogs 17.

IT CAN INFECT ANY PART OF THE BODY, Chest, Brain, Kidneys etc.

Clinical Presentation

In humans 75% of  the hydatid cysts cases are localize to the liver and develops as slowly growing mass (cysts) in the body usually filled with clear fluid (hydatid fluid)- (protein, albumin, Codounis, polydorides, Antigen-antibodies, and Alpha/beta/gamma globulin) 3. Patients could be symptomatic and usually presents with abdominal pain, abdominal tenderness, hepatomegaly, fever, jaundice, and poor appetite. If the cyst gets rupture in the body due to trauma or during surgical removal it can lead to anaphylactic reaction such as fever, pruritis, edema of lips and eyelids, dysponea, stridor 3, 18.

Differential Diagnosis

The hydatid liver cyst  appears as a complicated liver cyst, Amoebic hepatic Abscess, cholangio carcinoma, Hepatic Adenoma, primary hepatic carcinoma, and pyogenic hepatic abscess.

Laboratory Tests

Generally, routine laboratory tests do not show specific result. In patients with rupture of the cyst in the biliary tree, marked and transient elevation of cholestatic enzyme levels occurs, often in association with hypermylasemia and eosinophillia (up to 60%). Cystic echinoccosis is one of few parasitic infections in which the basis for laboratory diagnosis is primary serology 18.

It can infect your eye.

Imaging Studies

Radiographic examination is useful for cysts in the lungs, bone which appears as  calcified cysts. Ultrasonography is the procedure of choice when making the diagnosis of asymptomatic cystic echinoccosis because it is safe, non-invasive, and relatively inexpensive.  Ultrasonography is useful in longitudinal studies, such as monitoring the response of cysts to treatment and recording cyst growth rate 17.  

Various classifications exist of the ultrasonographic picture in cystic echinoccosis, the most widely used still being the one proposed by Gharbi in the early 1980s 19. In 2003, the World Health Organization informal working group on Echinoccosis (WHO-IWGE) proposed a standardized ultrasound classification based on the active-transitional-inactive status of the cyst as suggested by its sonographic appearance 20.   Cysts with a visible split wall inside (floating membrane or water lily sign) are pathognomonic, septated cysts, or cysts with a honey comb pattern, are likely to be echinococcal. Cysts with well-defined boarders and uniform anechoic contents are simple liver cysts . A solid heterogeneous mass is difficult to differentiate from granola mass or tumors 20.

Sheep and farm animals to Dogs and then to human.

Echocardiography may be used to detect Cardiac lesions

Computed tomography scanning has the advantage inspecting any organs in human body and detecting smaller cysts outside the liver .Sometimes differentiating parasitic from non parasitic cysts. However, the cost of CT scanning  fees is discouraging factor to so many patients who can not afford to pay .

Magnetic Resonance Imaging  (MRI) may have some advantage over CT scanning in the evaluation of post surgical residual lesions, recurrences, and selected extra hepatic infections, such as cardiac infections as it shows the soft tissues much better than CT scan 21.

Other tests

Endoscopic retrograde cholangiopanecreatography (ERCP) may be indicated in patients with cholestatic jaundice. This techniques may also be a therapeutic intervention when cysts communicating with the biliary tree can be basked out. This test can define the presence of a cyst in the pancreatic duct and distal common bile duct.

Medical care and treatment

Surgical removal of the cyst , chemotherapy are effective against cystic echinoccosis 22. If the cyst removed, puncture aspiration injection re-aspiration  is an option 23, 24, 25.  Puncture aspiration injection is one of the  methods that helps provide a direct diagnosis of the parasitic nature of the cyst 24, 26.

Prevention

In endemic areas, distribution of educational material in elementary schools regarding modes of transmission of the disease is helpful to increase knowledge about the nature and transmissibility of cystic echinoccosis. There are a lot of other prevention that you can find in the literature’s . Wild game is a problem in Canada and it needs to be regulated with the help of the infection control departments of each province. . Educational material should include information about proper disposal of sheep viscera in abattoirs and proximity to dogs and source of transmission 27.

Complications

The Hydatid cysts may rupture and the cyst content may be released into biliary or bronchial system. This may cause obstruction of the biliary or bronchial tree with several clinical complications such as; pneumonitis, pleural effusion, phenomothorax, secondary echinoccosis of the pleural and peritoneal cavity 28, 29.

Prognosis

Prognosis is generally good and depends on the cyst location. For instance, neither surgery nor medical therapy is generally effective for bone, especially spinal echinoccosis , Chemotherapy might help in this region. Surgery is very effective in most of other location of hydatid cyst in the human body 30.   

Discussion

Hydatid disease is anthropozoonosis with worldwide distribution including North Europe and North Canada 1-3. In North Canada both Echinococcus granulossus and cystic Echinococcus infections are detected 4, 5. The sylvatic variant (‘Sylvatic’ means ‘occurring in or affecting wild animals’.) The sylvatic cycle is the fraction of the pathogen population’s lifespan spent cycling between wild animalsand vectors. Humans are usually an incidental or dead-end host, infected by a vector seen in North America is more benign than the postural variant seen in countries that considered to be sources of HD 4-6. Liver and lung are the most organs involved with HD 7. The annual incidence rates  of diagnosed human cases per 100,000 inhabitants vary widely. HD causes not only illness but also productivity losses in human and agricultural animal population, and it can have large societal impact on endemic areas 7. The HD seen also in rare locations in the body such as muscles, bone, brain, heart and orbits 9-16. HD can affect any race, females are more prone than males to HD in some endemic countries, all ages are affected and children are affected in higher rates because are most likely to play with dogs 17. Cystic Echinoccosis can be diagnosed by serology 18.

HD can be confused with  a complicated liver cyst, amebic hepatic abscess and other hepatic masses 19-20. CT and MRI may displace the same finding as ultrasound, however calcification of the cysts wall or internal septa is easily detected with CT. It is widely accepted that abdominal CT, with its higher rate of accuracy, is the diagnostic tool of choice. However, MRI, due to its multi planar capabilities and the excellent contrast resolution for soft tissues, has a particular importance if the diagnosis of HD is questionable, because it is more accurate in demonstrating partial features and defining anatomical relationships 21-23.

The treatment option for HD of the liver depend on stage localization, size and complication of the cyst, and include non operative and operative method 27. The Echinococcal cyst may rapture and the cyst content may be released into biliary or bronchial system, and may cause several complications such as pneumonitis, pleural effusion, pneumothorax, secondary echinoccosis of the pleural and peritoneal cavity 29, 29. Prognosis is good and depend on the cyst location 30.

Conclusion

This case showed that hydatid cyst can reach a large size. Ultrasound is very useful in the study of the liver cysts and it is the first imaging tool to be used before sending the patient to CT and MRI examination. Sonographers should be familiar with the HD and Hydatid cyst classifications in the liver. Hepatic hydatid disease causes highly variable symptoms and signs, and can be found incidentally in an asymptomatic patient. The symptoms and signs may be caused by a toxic reaction to the parasite or by local and mechanical effects, depending on the location and nature of the cysts and the presence of complications. Early diagnosis and proper treatment will help to reduce the complication rate and prevent recurrence.

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Thank you for reading

Steve Ramsey, PhD- Calgary – Alberta